Got a USB wireless set sitting idle at the moment, hope it still works (threw the receiver at the wall out of frustration when it wouldn't work with my MX700 :)).
Wires forever, must have 50m of the stuff running around the house.

Main factor in price is the extra RAM and harddisk space plus extra software (Photoshop ain't cheap and uses a LOT of RAM) and of course a good screen for it (17" TFT).

In all I'd end up more than doubling the 500 pricetag.

I'm actually looking at an Inspiron 6000 at the moment. Slightly larger but more economical. What I get will depend on which models are discounted around the time I get the funds together :)